The engineer's essential function is decision making. In this activity he should tend toward the optimization of the systems he designs. The scale of values on which established practice is based reflects the consensus of the profession. This does not guarantee rationality, which is identified with optimization in this paper. The paper explores conditions for rationality and the corresponding scales of utility. A distinction is made between descriptive and normative utilities. The latter quantitatively specifies an order of preference which defines an ethical system. These concepts are extended to make them applicable to a group of individuals. An ethics is proposed which maximizes the expected happiness (felicity) of all sentient beings. Professional, social, and theological implications of this ethical system are examined and it is compared with other systems. Finally, its implications in the drafting of quality standards and building codes are discussed.